Guide to Computational MetaInfo

Overview of metadata organization for computation

NOMAD stores all processed data in a well defined, structured, and machine readable format, known as the archive. The schema that defines the organization of (meta)data within the archive is known as the MetaInfo. See Explanation > Data structure for general information about data structures and schemas in NOMAD.

The following diagram is an overarching visualization of the most important archive sections for computational data:

archive
├── run
│    ├── method
│    │      ├── atom_parameters
│    │      ├── dft
│    │      ├── forcefield
│    │      └── ...
│    ├── system
│    │      ├── atoms
│    │      │     ├── positions
│    │      │     ├── lattice_vectors
│    │      │     └── ...
│    │      └── ...
│    └── calculation
│           ├── energy
│           ├── forces
│           └── ...
└── workflow2
     ├── method
     ├── inputs
     ├── tasks
     ├── outputs
     └── results

Entire subsections of NOMAD's schema can be browsed using the MetaInfo Browser:

• run base schema: MetaInfo Browser > Entry > run
• runschema full schema for run: MetaInfo Browser > runschema
• workflow2 base schema: MetaInfo Browser > Entry > workflow2
• simulationworkflowschema full computational schema for workflow2: MetaInfo Browser > simulationworkflowschema

The most important section of the archive for computational data is the run section, which is divided into three main subsections: method, system, and calculation. method stores information about the computational model used to perform the calculation. system stores attributes of the atoms involved in the calculation, e.g., atom types, positions, lattice vectors, etc. calculation stores the output of the calculation, e.g., energy, forces, etc.

The workflow section of the archive then stores information about the series of tasks performed to accumulate the (meta)data in the run section. The relevant input parameters for the workflow are stored in method, while the results section stores output from the workflow beyond observables of single configurations. For example, any ensemble-averaged quantity from a molecular dynamics simulation would be stored under workflow/results. Then, the inputs, outputs, and tasks sections define the specifics of the workflow. For some standard workflows, e.g., geometry optimization and molecular dynamics, the NOMAD normalizers For non-standard workflows, the parser (or more appropriately the corresponding normalizer) must populate these sections accordingly. See Explanation > Workflows for more information about the general structure of the workflow section, and How-to Guides > Customization > Define workflows for instructions on how to upload custom workflows to link individual entries in NOMAD.

Attention

We are currently performing a complete refactoring of the computational MetaInfo schema. The new schema will be populated under the data section of the archive: MetaInfo Browser > Entry > data. A preliminary version of the full schema can be browsed in MetaInfo Browser > nomad_simulations.

Further information can be found within the schema plugin docs: nomad-simulations Docs.